Google Earth’s prowling map cars have helped produce the latest image of Boston’s leaky gas pipelines and offered an example of how sensors are starting to make environmental information more public.
The map, released Wednesday by the Environmental Defense Fund, shows methane seeping from thousands of aging pipes in the city. The leaks are all low-level, and not seen as severe enough to explode. But customers pay for the leaked fuel, and the methane — the primary component of natural gas — is a powerful greenhouse gas helping cause climate change.
“Pound for pound, methane is 120 times more potent than carbon dioxide,’’ Steve Hamburg, chief scientist of the environmental group, said on a conference call. “If we can better understand the source and quantity of the emissions, that gives us the opportunity to mitigate.’’
This is not the first illustration of the gaseous seepage from Boston’s old, corroding pipelines. Boston University Professor Nathan Phillips and his students drove all of the city’s 785 miles in a black hatchback equipped with a gas sensor in 2012, finding about 3,300 leaks. And the Conservation Law Foundation has mapped the leaks reported to the Massachusetts Department of Public Utilities, showing about 4,000 of them.
The EDF study “builds on that work,’’ said Hamburg. The researchers mounted sensors on three Google Earth Street View map cars, which traversed many — though not all — of the city streets in the spring of 2013. In addition to pinpointing leaks that, in some areas, occurred every couple of blocks, the EDF attempted to calculate the “flux rate’’ of each leak, to determine which holes in the pipes are leaking the most natural gas.
By doing so, the National Grid utility could schedule repair of the most serious leaks first. “We calculate that two to three times more gas can be reduced by prioritizing these larger leaks,’’ said Hamburg.
“You are always going to be replacing pipes somewhere. What matters is which pipes you are replacing, and how much pipe you are replacing and how quickly you are doing it,’’ said Seth Kaplan, vice president of the Conservation law Foundation. “This kind of information highlights where it needs to happen, how much, and how quickly.’’
BU’s Phillips said the fact that Boston’s utilities are in poor repair is not news, but the EDF’s attempt to estimate the flow of each leak “would truly be major.’’ And it is an example of how technology is bringing better and more information to the public.
“Taking this information and making it more publicly accessible is an important thing to do,’’ Phillips said. “It’s raising the awareness of this issue.’’
Such data used to be buried in the reports of scientists or in the records of utility companies. As it becomes more accessible to the public, the information helps foster understanding of environmental concerns, said Mark Brownstein, associate vice president at EDF.
“I think what you are seeing is an evolution over time. Ten years ago, people were not focused on [leaks] at all, except for safety. As we’ve learned more about methane in the atmosphere, and what that means for our climate, we are redoubling our efforts to understand where the methane comes from.’’
The growing concerns about gas line leaks prompted the Massachusetts legislature to approve a plan to require faster repairs, and Governor Deval Patrick signed the bill June 26.
Kaplan said Massachusetts is “ahead of the curve’’ on the issue, thanks to the reports on the leaks and the legislative interest they stirred.
It is unclear, however, what will be done as a result of the mapping, acknowledged Susan Fleck, vice president for pipeline safety at National Grid. The company aggressively fixes reported leaks based on the threat to public safety — called “type one’’ and “type two’’ leaks — she said. The lower-level “type three’’ chronic leaks mapped by the EDF are generally fixed according to a long-term schedule of pipeline replacement, or if street work exposes the pipes, she said.
“When we look at these type three leaks, we try to do most of these leaks under these programs rather than make individual repairs. We think that’s the most efficient,’’ she said. “This [mapping] is a pilot program. Exactly how this is going to phase in, I can’t say definitely now.’’